The propagation properties of high frequency ultrasonic waves in steel 12Cr2MoWVTiB(G102) and 12Cr1MoV were calibrated and statistic calculation of calibration errors was carried out. Results showed that the maximum occasional errors of scale thickness measurement were respectively 0.050mm and 0.030mm for steel 12Cr1MoV and G102. The origins of the errors were pointed out.